A frag missile (Blast 5) hits the front of an open topped ork wartrukk which is carrying a driver, a gunner and 12 ork boyz. How many orks are caught in the blast?

All of them, per RAW

Page 213 in the rulebook.

All of them, per RAW

Page 213 in the rulebook.

No. That's not what the rulebook says.

"Additionally, passengers mounted in Open-Topped vehicles are struck by any Blast or Spray attacks which they would be in range of."

The phrase giving me trouble is: "... which they would be in range of."

How does one determine whether the passengers are in range of the blast/spray? If the missile hits the front of the truck, how far is it to the back of the truck and where in the truck are those dozen ork boyz standing.

Blast radius is blast radius

Obviously Rule #1 would apply, but I'm fairly certain my GM would rule that everyone inside a blast radius would get hit in such an instance.

If the ork trucks look anything like this : http://www.dakkadakka.com/gallery/16819-ork%20truck%20L%252Fside.html - then that small piece of plating isn't going to take that much of the blast if the driver and gunner is hit head on.

I guess my question is, how do we know how much of any given vehicle is covered by the blast radius? I mean, I have no idea how big an ork wartrukk actually is from the front of the hood to the rear of the passenger bed.

Well, I have two of the TT models and they're not really to scale (no 40k transport is) but I'd presume not everyone in the back is hit. Being hit in the "front" is also a bit...unhelpful, there's a rather large gap between the front bunker and the engine. Hit the engine and I'd presume 2/3's of the passangers are hit, the bumper only 1/3.

Hrmm!

A Wartrukk is counted as being enormous, While those things aren't even close enough to be standardized, they do fall into the same category as a sentinel. Sentinels range in height between 4.8-5.2 meters, roughly the length of a modern military 5-ton truck. Using this comparison you could say the average frag grenade (3 meter radius) would be able to catch everyone if it landed dead center. You do have to use a bit of common sense here and say some passengers will have the advantage of cover (the driver would probably get some by a grenade going off in the bed) I did the comparison with different weapons, blast radius, and comparative vehicle lengths. If you add 3 to a weapons blast radius and then compare it against the size of the vehicle, then you can safely say a direct hit will hit all exposed passengers. If we are talking a directional hit and the resulting splash then the math changes and gets to the point where you really just have to look at the layout of the vehicle. In addition, this isn't always perfect. A frag missile striking a howdah on the gargantuan squiggoth is unlikely to hit every single exterior ork so you might decrease the number of targets hit by 1d10?

For the sake of speed I'd just do the blast rating +3 compared against vehicle size rating.

Sentinels are 5 meters?! Since when? Tall? Long? because it's basically two legs, a cockpit and a chin mounted gun. That's all a sentinel has. How is it 5 meters?

Of course you should count any parts of the vehicle as parts of the cover, but we were talking front not into the bed of the trukk. Some of the orks would probably act as cover for the other orks further back though.

Sentinel Scout Vehicle:

Height: 4.8m

Width: 2.3m

Weight: 7 tonnes

Not so small when you think. Info taken from Lexicanum.

Never seen a picture of a sentinel that tall, then again sentinels aren't exactly the most portrayed vehicle in 40k. At least not with humans to do a size comparison.

Sounds weird considering the size of a human, the size of the cockpit and the inverse jointed legs. Regardless, if you hit the legs the cockpit is fine then! As long as you don't hit knee'ish height.

Edit: upon reflection it's probably just me being used to seeing them on the tabletop (with guardsman inside) and the size not being translatable from fluff to tabletop requirements.

True, my bad. I should have posted references and such on sentinel height. I also foolishly forgot to address the actual issue of does the front striking missile get all the orks? Yes, I'd say. The blast 5 rating is sufficient to catch the entire length of the vehicle. I guess the biggest point of debate is what sort of cover does everyone get, and can you use your big green friends as cover?